Perhaps best known for his own bands Time Zone (with Martin Hathaway, Stuart Hall etc) and Inner Space (with Chris Biscoe, Rachel Musson, Olie Brice, Gary Willcox), Speyer has been leading and composing for both groups since 2003, developing and honing the distinct sound of each. Both bands have toured the UK extensively and released two albums each to date. Time Zone played a week at Ronnie Scotts opposite Airto Moreira, and Lancaster, Manchester, Scarborough and Lichfield Jazz Festivals.

Speyer spent some extended periods in Santiago de Cuba (totalling over a year between 2000 and 2009) - studying percussion, recording and transcribing, and working with local Son bands. In 2005 he recorded three Time Zone pieces with a Cuban band, one of which was later released on the Babel label compilation Now’s the Time II. And his collaboration Proyecto Evocación, with master percussionist Rafael Cisneros (of Ballet Folklorico Cutumba) featured live on various stages in Santiago's week-long Festival del Caribe, resulting in the CD Roots en Route – Raices en Viaje (2010 Spherical Records).

Returning to his small group jazz roots, Speyer recently re-formed his own Loz Speyer Quartet, playing a mix of Thelonious Monk's music and his own jazz compositions.

As a composer for larger ensembles, Loz was a founder member of the innovative 12-piece Rare Mix (1995-2000) which brought together the unusual combination of Jason Yarde, Brian Abrahams, Pete Saberton, Ben Davis, Martin Hathaway, Simon Picard, Julian Seigel, Jim Dvorak etc... and featured collective compositions by this star studded team of bandleaders. In 2000 Rare Mix recorded an album Everything is Possible, yet to be released...

Loz Speyer's big band arrangements have been performed and recorded by jazz orchestras at the Guildhall School of Music and Morley College, as well as by Rare Mix... and his extended arrangement for Octet of the Bastille Concerto, composed by Clifford Jarvis' father, formed a centrepiece in the memorial concert at the Spitz in honour of this great jazz drummer.

His teaching work, which he fulfills with a passion, ranges from small group trumpet lessons and whole class band workshops with school children in Haringey, to leading workshops and rehearsing his own compositions with diploma students at the Guildhall School of Music.